In order to stop people spamming roles with hundreds of suggestions, how about a limit of 5 suggestions per search (you can add more but you'd have to go back and reopen the search, not a problem for most users but slows down spammers) and an overall suggestions limit per 24 hours for each user.
Please no limits on me. It all depends on the characters I'm trying to cast. And I'm being careful who I cast according to their backgrounds, ages and such.